# Java program for longest palindrome in an array

## Longest Palindrome in an Array in Java

Here, in this page we will discuss the program to find the longest palindrome in an array in java programming language. We are given with an array and need to print the longest palindromic element in the given input array.

## Method Discussed :

• Method 1 : Using Naive Approach
• Method 2 : Using Sorting

## Method 1 :

• Create a function ispalindrome(int n), it will return 1 if the passing number is palindrome otherwise return 0.
• Inside the main function, create a variable say res = -1, that hold the maximum palindrome number.
• Run a loop from [0, n),  and check if(ispalindrome(arr[i]) && res<arr[i]), then set res = arr[i].
• Print the value of res.

### Method 1 : Code in Java

Run
```import java.util.*;

class Main
{
// Function to check if n is palindrome
static boolean isPalindrome(int n)
{
// Find the appropriate divisor
// to extract the leading digit
int divisor = 1;
while (n / divisor >= 10)
divisor *= 10;

while (n != 0) {
int x = n / divisor;
int y = n % 10;

// If first and last digits are
// not same then return false
if (x != y)
return false;

// Removing the leading and trailing
// digits from the number
n = (n % divisor) / 10;

// Reducing divisor by a factor
// of 2 as 2 digits are dropped
divisor = divisor / 100;
}
return true;
}

// Function to find the largest palindromic number
static int largestPalindrome(int []A, int n)
{
int res = -1;

for (int i = 0; i < n; i++) { // If a palindrome larger than the currentMax is found
if (A[i] > res && isPalindrome(A[i]))
res = A[i];
}

// Return the largest palindromic number from the array
return res;
}

// Driver program
public static void main(String []args)
{
int []A = { 121, 2322, 54545, 999990 };
int n = A.length;

// print required answer
System.out.println(largestPalindrome(A, n));
}

}```

`54545`

## Method 2 :

In this method we first sort the array and then start traversing the array from end, and return the element that satisfy the condition, that it is palindrome.

• Sort the array using inbuilt sort() function.
• Start traversing from end of the array,
• Print the element if it is palindrome.
• If no element found then print -1.

### Method 2 : Code in Java

Run
```import java.util.*;
class Main
{
// Function to check if n is palindrome
static boolean isPalindrome(int n)
{
// Find the appropriate divisor
// to extract the leading digit
int divisor = 1;
while (n / divisor >= 10)
divisor *= 10;

while (n != 0) {
int x = n / divisor;
int y = n % 10;

// If first and last digits are
// not same then return false
if (x != y)
return false;

// Removing the leading and trailing
// digits from the number
n = (n % divisor) / 10;

divisor = divisor / 100;
}
return true;
}

// Function to find the largest palindromic number
static int largestPalindrome(int []A, int n)
{
Arrays.sort(A);
for (int i = n-1; i >= 0; i--) {
// If a palindrome larger than the currentMax is found
if (isPalindrome(A[i]))
return A[i];
}

// Return the largest palindromic number from the array
return -1;
}

// Driver program
public static void main(String []args)
{
int []A = { 121, 2322, 54545, 999990 };
int n = A.length;

// print required answer
System.out.println(largestPalindrome(A, n));
}

}```

`545545`

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### 4 comments on “Java program for longest palindrome in an array”

• Gokul

// Online Java Compiler
// Use this editor to write, compile and run your Java code online

class HelloWorld {

public static int[] SortArray()
{
int arr[]={2,1,3,4,5,50};
int len=arr.length;
int temp;
for(int i=0;i<len;i++)
{
for(int j=i+1;jarr[j])
{
temp=arr[i];
arr[i]=arr[j];
arr[j]=temp;
}
}
}

return arr;
}

static boolean checkPalin(int num)
{
int rev=0,temp=num;

if(num<=9)
return true;
while(num!=0)
{
int rem=num%10;
rev=rev*10+rem;
num/=10;
}

return temp==rev;
}

public static void main(String[] args) {

int a[]=SortArray();
int log_palin=-1;

for(int i=0;i<a.length;i++)
{
if(checkPalin(a[i]))
{
log_palin=a[i];
}
}
System.out.print(log_palin);
}

}

• Dhivya

import java.util.Scanner;

public class palindrome_number {
public static boolean isplaindrome(int a){
int num=a;
int res=0;
int rem=0;
while(num !=0){
rem= num%10;
res= (res*10)+rem;
num=num/10;
}
if( res == a){
return true;
}
else
return false;
}
public static int largestPalindrome(int arr[], int n){
int c =-1;

for(int i=0;ic && isplaindrome(arr[i])){
c = arr[i];
}

}
return c;
}
public static void main(String[] args) {
Scanner s= new Scanner(System.in);
int n= s.nextInt();
int arr[]= new int[100];
for( int i=0;i<n;i++)
arr[i] = s.nextInt();
System.out.println(largestPalindrome(arr,n));

}
}

• Mahesh

int[]a={11,333,22,55,45,232,545,66,456,454,5655,12,12232,45454,6766,454,344,2333,11111,123,34233,455};
Arrays.sort(a);
for(int i=a.length-1;i>=0;i–){
if(isPalindrome(a[i])){
System.out.println(a[i]);
break;
}
}
}
static boolean isPalindrome(int n){
String s=Integer.toString(n);
int i=0,j=s.length()-1;
while(i<j){
if(s.charAt(i)!=s.charAt(j)){
return false;
}
i++;
j–;
}
return true;
}

• lasic

import java.util.Arrays;
import java.util.Scanner;

public class array_palindrome {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println(“Enter the Range”);
int n = sc.nextInt();
int a[] = new int[n];
int z[]=new int[n];
int q=0;
for (int i = 0; i < n; i++) {
a[i] = sc.nextInt();
}
for(int i=0;i<n;i++)
{
int b=a[i];
String s="";
while(b!=0)
{
int remainder=b%10;
s= s +remainder;
b=b/10;
}
if(a[i] == Integer.parseInt(s))
{
z[q]=a[i];
q++;
}
}
Arrays.sort(z);
try {
System.out.println(z[q – 1]);
} catch (ArrayIndexOutOfBoundsException e) {
System.out.println("There is no palindrome");
}

}}